1. Field of Invention
This invention relates generally to solar panels, and more particularly to methods and apparatus for monitoring the condition of solar panels.
2. Description of Related Art
Solar panels are used in solar power generation systems to produce electrical power. Solar panels generally produce direct current (DC) power which may be used to charge a bank of batteries. Alternatively, the DC power may be supplied to a power converter that converts the DC power into AC power suitable for supplying an AC power grid, for example.
Solar panels are generally mounted outdoors for exposure to the sun's radiation. Being outdoors they are also exposed to contamination by dirt and debris such as dust, sticks, leaves, or snow for example. Such contamination may not physically damage the solar panels, but can cause a reduction in electrical power output for a given insolation as it can reduce the amount of radiation that is able to reach the active areas of the panels.
In addition, as solar panels age their power output decrease by perhaps as much as 0.5% per year.
In general it is not always possible to determine whether a reduction in power output is due to lower irradiation levels, lower temperatures, contamination of the panels, or ageing. Since solar panels are often mounted inaccessible locations, regular visual inspection is not always feasible.